Calvert Cliffs Nuclear Power Plant shut down its unit 2 reactor at approximately 5 p.m. Thursday, after a control rod was intentionally inserted into the reactor core for testing and it was determined that there was an electrical problem with the control rod, according to officials.

U.S. Nuclear Regulatory Commission spokesman Neil Sheehan said in an email Friday morning that the Lusby plant’s technical specifications require a shutdown if the control rod cannot be realigned within six hours. NRC resident inspectors at the plant were notified immediately, and “the controlled shutdown occurred without any complications and there were no impacts on the public or plant staff,” he wrote.

Kory Raftery, plant spokesman, said in an email Friday that CENG’s plant operators manually shut down unit 2 to perform the required maintenance and “followed their training and procedures and the plant shut down as expected.”

“The plant is in stable condition,” the email continues. “... The safety of Calvert Cliffs and the public was maintained at all times during the shutdown.”

After performing maintenance on the unit, at approximately 8:10 a.m. Tuesday, Raftery said the unit was successfully synchronized to the electrical grid. At around 9:10 a.m., Raftery said the unit was at 30 percent power and would continue to escalate to full power over the next 12 to 24 hours as the operators receive the proper indications in the control room for start-up.

Sheehan said in the email the plant is equipped with 77 control rods designed to control the “fissioning of atoms in the reactor.” In August 2012, Calvert Cliffs Unit 1 experienced a single control rod drop. “As we said after that event,” he said in the email, “nuclear power plants have specific procedures on what to do if a control rod drop occurs.”